This invention relates to novel substituted cyclopentane compounds and derivatives thereof useful as neuraminidase inhibitors, to pharmaceutical compositions containing said compounds useful for the prevention, treatment or amelioration of viral, bacterial and other infections, and to methods of using said compounds. The present invention is also concerned with novel intermediates or precursors for producing the novel substituted cyclopentane compounds of the present invention.
Despite the wealth of information available, influenza remains a potentially devastating disease of man, lower mammals, and birds. No effective vaccine exists and no cure is available once the infection has been initiated.
Influenza viruses consist of eight pieces of single stranded RNA, packaged in orderly fashion within the virion. Each piece codes for one of the major viral proteins. The replication complex is enclosed with a membrane composed of matrix protein associated with a lipid bilayer. Embedded in the lipid bilayer are two surface glycoprotein spikes, hemagglutinin (HA) and the enzyme neuraminidase (NA). All of the viral genes have been cloned and the three-dimensional structures of the surface glycoproteins have been determined.
Influenza viruses continually undergo antigenic variation in the two surface antigens, HA and NA, toward which neutralizing antibodies are directed. For this reason, vaccines and a subject""s natural immune system have not been very effective. Attention is now being directed to finding other potential antiviral agents act ing at other sites of the virion. This invention is directed to novel compounds which are useful in inhibiting the viral surface enzyme NA.
Furthermore, many other organisms carry NA. Many of these NA-possessing organisms are also major pathogens of man and/or mammals, including Vibraeo cholerae, Clostridium perfringes, Streptococcus pneumonia, Arthrobacter sialophilas, and other viruses, such as parainfluenza virus, mumps virus, Newcastle disease virus, fowl plague virus, and Sendai virus. Compounds of this invention are also directed to inhibiting NA of these organisms.
In viruses, NA exists as a tetramer made of four roughly spherical subunits and a centrally-attached stalk containing a hydrophobic region by which it is embedded in the organism""s membrane. Several roles have been suggested for NA. The enzyme catalyzes cleavage of the xcex1-ketosidic linkage between terminal sialic acid and an adjacent sugar residue. Removal of the sialic acid lowers the viscosity and permits access of the virus to the epithelial cells. NA also destroys the HA receptor on the host cell, thus allowing elution of progeny virus particles from infected cells.
Research indicates that the active site for influenza neuraminidase remains substantially unchanged for the major strains of influenza. For example, a comparison of sequences from influenza A subtypes and influenza B shows conserved residues with crucial structural and functional roles. Even though the sequence homology is only about 30%, many of the catalytic residues are conserved. Furthermore, the three-dimensional structures of influenza A and B neuraminidases have been determined. Superposition of the various structures shows remarkable structural similarity of the active site. Since the active site amino acid residues are conserved in all known influenza A neuraminidases that have been sequenced so far, an inhibitor that is effective against different strains of influenza A and/or B neuraminidase can be designed based on the three-dimensional structure of a neuraminidase.
In general, the role of NA is thought to be for the mobility of the virus both to and from the site of infections. Compounds that inhibit neuraminidase""s activity may protect a subject from infection and/or cure a subject once infection has set in. It is a further object of this invention to provide a method of using compounds of this invention for treating and/or curing a viral infection.
Analogs of neuraminic acid, such as 2-deoxy-2,3-didehydro-N-acetylneuraminic acid (DANA) and its derivatives are known to inhibit HA in vitro; however, these compounds are inactive in vivo. Palese and Schulman, in CHEMOPROPHYLAXIS AND VIRUS INFECTION OF THE UPPER RESPIRATORY TRACT, Vol. 1 (J. S. Oxford, Ed.), CRC Press, 1977, at PS 189-205.
Von Itzstein et al. (PCT Publication WO 91/16320) describes cyclohexane analogs of xcex1-D-neuraminic acid of the formula 
wherein:
A is O, C or S in Formula (a), and N or C in Formula (b);
R1 is CO2H, PO3H2, NO2, SO2H, SO3H, tetrazolyl-, CH2CHO, CHO, or CH(CHO)2;
R2 is H, OR6, F, Cl, Br, CN, NHR6, SR6 or CH2X, where X is NHR6 halogen, or OR6;
R3 and R3xe2x80x2 are H, CN, NHR6, SR6, xe2x95x90NOR6, OR6, guanidino, NR6;
R4 is NHR6, SR6, OR6, CO2R6, NO2, C(R6)3, CH2CO2R6, CH2NO2 or CH2NHR6;
R5 is CH2YR6, CHYR6CH2YR6 or CHYR6CHYR6CH2YR6;
R6 is H, acyl, alkyl, allyl, or aryl;
Y is O, S, NH, or H;
and parmaceutical salts thereof, useful as antiviral agents
In addition, certain benzene derivatives are suggested in U.S. Pat. No. 5,453,533 as being inhibitors of influenza virus neuraminidase and various others are disclosed in U.S. patent application Ser. No. 08/413,886. Yamamoto et al. describe various sialic acid isomers as having inhibitory activity against neuraminidase in Synthesis of Sialic Acid Isomers With Inhibitory Activity Against Neuraminidase, TETRAHEDRON LETTERS, Vol. 33, No. 39, pp. 5791-5794, 1992.
WO 96/26933 to Gilead Sciences, Inc. describes certain 6-membered ring compounds as possible inhibitors of neuraminidase.
However, none of these references disclose the cyclopentane derivatives of the present invention.
An aspect of the present invention is directed to compounds represented by the formula: 
wherein
X is CH2, O or S;
R1 is H, OH, NH2, or OR11;
R9 is CO2H, SO3H, PO3H2, NO2, esters thereof, or salts thereof;
R2 is H, 
each of R3 and R8 individually is H, (CH2)nCO2R10, (CH2)mOR10, CON(R10)m, (CH2)nN(R10)m, CH(R10)m, (CH2)n(R10)m, CH2CH(OR10)CH2OR10, CH(OR10)CH(OR10)CH2OR10, CH2OR10, CH(OR10)CH2NHR10, CH2CH(OR10)CH2NHR10, CH(OR10)CH(OR10)CH2NHR10, or NR10C(xe2x95x90NR10)N(R10)m; provided that at least one of R2, R3 and R8 is other than H;
R4 is H, (CH2)nOH, (CH2)nNH2, (CH2)nC(xe2x95x90NH)NH2, (CH2)nNHC(xe2x95x90NR7)NH2, (CH2)nCN or (CH2)nN3;
R5 is H, lower alkyl, branched chain alkyl, cyclic alkyl or CF3;
R7 is H, OH, CN, NH2 or NO2;
each R10 individually is H, lower alkyl, lower alkylene, branched alkyl, cyclic alkyl, substituted cyclic alkyl, (CH2)n aromatic, (CH2)n-substituted aromatic, and when m is 2 both R10 groups can also be interconnected to form an N-heterocyclic ring;
R11 is lower alkyl, branched alkyl, or (CH2)m aromatic;
m is 1 or 2; and
n is 0-4; and
further provided that when X is O or S, R3 and R8 is other than CH(OR10)CH(OR10)CH2OR10;
and phramaceutically acceptable salts thereof.
The present invention is also concerned with compositions for inhibiting influenza virus neuraminidase comprising a pharmaceutically acceptable carrier and an amount effective for inhibiting influenza virus neuraminidase of a compound as defined above.
A further aspect of the present invention involves a method for inhibiting influenza virus that comprises administering to a patient in need thereof a compound as defined above in an amount effective for inhibiting influenza virus neuraminidase.
A still further aspect of the present invention is concerned with treating influenza virus infection comprising administering to a patient in need thereof a compound as defined above in an amount effective for inhibiting influenza virus neuraminidase.
The present invention is also concerned with methods for producing the compounds defined above.
An aspect of the present invention is directed to compounds represented by the formula: 
wherein
X is CH2, O or S;
R1 is H, OH, NH2, or OR11;
R9 is CO2H, SO3H, PO3H2, NO2, esters thereof, or salts thereof;
R2 is H, 
each of R3 and R8 individually is H, (CH2)nCO2R10, (CH2)mOR10, CON(R10)m, (CH2)nN(R10)m, CH(R10)m, CH2)n(R10)m, CH2CH(OR10)CH2OR10, CH(OR10)CH(OR10)CH2OR10, CH2OR10, CH(OR10)CH2NHR10, CH2CH(OR10)CH2NHR10, CH(OR10)CH(OR10)CH2NHR10, or NR10C(xe2x95x90NR10)N(R10)m;
provided that at least one of R2, R3 and R8 is other than H;
R4 is H, (CH2)nOH, (CH2)nNH2, (CH2)nC(xe2x95x90NH)NH2, (CH2)nNHC(xe2x95x90NR7)NH2, (CH2)nCN or (CH2)nN3;
R5 is H, lower alkyl, branched chain alkyl, cyclic alkyl or CF3;
R7 is H, OH, CN, NH2 or NO2;
each R10 individually is H, lower alkyl, lower alkylene, (CH2)n aromatic, branched alkyl, cyclic alkyl, substituted cyclic alkyl, (CH2)n-substituted aromatic, and when m is 2 both R10 groups can also be interconnected to form an N-heterocyclic ring;
R11 is lower alkyl, branched alkyl, or (CH2)m aromatic;
m is 1 or 2; and
n is 0-4; and
further provided that when X is O or S, R3 and R8 is other than CH(OR10)CH(OR10)CH2OR10;
and pharmaceutically acceptable salts thereof.
Concerning R10 when m=2, each R10 can be the same or different.
The lower alkyl groups contain 1 to about 8 carbon, and preferably 1 to about 3 carbon atoms, and can be straight, branched-chain or cyclic saturated aliphatic hydrocarbon groups.
Examples of suitable alkyl groups include methyl, ethyl and propyl. Examples of branched alkyl groups include isopropyl and t-butyl. Examples of suitable cyclic aliphatic groups typically contain 3-8 carbon atoms and include cyclopentyl and cyclohexyl. The aromatic or aryl groups are preferably phenyl or alkyl substituted aromatic groups (aralkyl) such as phenyl C1-3 alkyl such as benzyl.
Examples of substituted cycloalkyl groups include cyclic aliphatic groups typically containing 3-8 carbon atoms in the ring substituted with alkyl groups typically having 1-6 carbon atoms and/or hydroxy group. Usually 1 or 2 substituted groups are present.
The lower alkylene group can be straight, branched chain or cyclic unsaturated hydrocarbon group and contains 2-8 carbon atoms and preferably 2-3 carbon atoms. Examples of alkylene groups are vinyl, 1-propenyl, allyl, isopropenyl, 2-methyl-2-propenyl and cyclopentenyl.
The N-heterocyclic rings contain 3-7 atoms in the ring. The heterocyclic rings can be substituted such as with a lower alkyl group. Examples of suitable heterocyclic groups are pyrrolidino, azetidino, piperidino, 3,4-didehydropiperidino, 2-methylpiperidino and 2-ethylpiperidino.
Pharmaceutically acceptable salts of the compounds of formula (I) include those derived from pharmaceutially acceptable, inorganic and organic acids and bases. Examples of suitable acids include hydrochloric, hydrobromic, sulphuric, nitric, perchloric, fumaric, maleic, phosphoric, glycollic, lactic, salicyclic, succinic, toluene-p-sulphonic, tartaric, acetic, citric, methanesulphonic, formic, benzoic, malonic, naphthalene-2-sulphonic, trifluoroacetic and benzenesulphonic acids.
Salts derived from appropriate bases include alkali such as sodium and ammonia.
Examples of some specific compounds within the scope of the present invention are:
cis-3-[(methylcarbonylamino)methyl]cyclopentanecarboxylic acid;
trans-3-amino-c-4-(methylcarbonylamino)methyl-r-cyclopentanecarboxylic acid;
trans-3-{[(amino)(imino)methyl]amino}-c-4-[(methylcarbonylamino)methyl]cyclopentan-r-carboxylic acid;
4(3-{[(amino)(imino)methyl]amino}-3xcex1-[(2-hydroxy-1-methylcarbonyl-amino)ethyl]-1-cyclopentanecarboxylic acid;
sodium 3xcex2-{[amino)(imino)methyl]amino}-4xcex1-[(2-hydroxy)(1-methylcarbonylamino)ethyl]cyclopentan-r-carboxylate;
trans-3-amino-trans-1-hydroxy-cis-4[(hydroxymethyl)(methylcarbonylamino)methyl]cyclopentan-r-carboxylic acid;
trans-3-{[(amino)(imino)methyl]amino}-trans-1-hydroxy-cis-4-[(2-hydroxymethyl)(1-methylcarbonylamino)ethyl]cyclopentan-r-carboxylic acid;
3xcex2-amino-4xcex1-[(1-methylcarbonylamino)(2,3,4-trihydroxy)butyl]cyclopentancarboxylic acid;
3xcex2-{[(amino)(imino)methyl)amino}-4xcex1-[(1-methylcarbonylamino)(2,3,4-trihydroxy)butyl]-cyclopentancarboxylic acid;
cis-3-{[(amino)(imino)methyl]amino)-trans-1-hydroxy-trans-4-[(1-methylcarbonylamino)(2-trifluoromethyl-carbonyloxy)ethyl]cyclopentan-r-carboxylic acid;
t-3-amino-c-4-[(1-methylcarbonylamino)(2-phenylmethoxy)ethyl]-t-1-hydroxycyclopentan-r-carboxylic acid;
c-3-{[(amino(imino)methyl]amino}-t-1-hydroxy-t-4-{(methylcarbonylamino)([(methyl)-(methoxy)amino]carbonyl}methyl}cyclopentan-r-carboxylic acid;
3xcex2-{[(amino)(imino)methyl]amino}-4xcex1-{{4-[(methoxy)(methyl)amino]1-(methylcarbonylamino-2-oxo}butyl}cyclopentancarboxylic acid;
t-3-{[(amino)(imino)methyl]amino}-c-4-[(diethylaminocarbonyl)(methylcarbonylamino)methyl]-t-1-hydroxycyclopentan-r-carboxylic acid;
t-3-amino-c-4-[(di-n-propylaminocarbonyl)(methylcarbonylamino)methyl]-t-1-hydroxy-cyclopentan-r-carboxylic acid;
t-3-{[(amino)(imino)methyl]amino}-c-4-[di-n-propylaminocarbonyl)(methylcarbonylamino)methyl]-t-hydroxycyclopentan-r-carboxylic acid;
c-3-{[(amino)(imino)methyl]amino}-t-4-[(di-n-propylaminocarbonyl)(methylcarbonylamino)methyl]-t-1-hydroxycyclopentan-r-carboxylic acid;
3xcex2-{[(amino)(imino)methyl]amino}-4xcex1-[(di-n-propylaminocarbonyl)(methylcarbonylamino)-methyl)cyclopentancarboxylic acid;
3xcex2-{[(amino)(imino)methyl]amino}-4xcex1-[(methylcarbonylamino)(3-pentylaminocarbonyl)methyl]cyclopentancarboxylic acid;
3xcex2-{[Amino)(imino)methyl]amino}-4xcex1-[(diethylaminocarbonyl)(methylcarbonylamino)methyl]cyclopentancarboxylic acid;
3xcex2-{1[(Amino)(imino)methyl]amino}-4xcex1-{[(ethyl)(propyl)aminocarbonyl](methyl-carbonylamino)methyl}cyclopentancarboxylic acid;
3xcex2-{([(Amino)(imino)methyl]amino}-4xcex1-{[(ethyl)(propyl)aminocarbonyl](methyl-carbonylamino)methyl}cyclopentancarboxylic acid;
3xcex2-{[(Amino)(imino)methyl]amino}-4xcex1-[1-(1-methylcarbonylamino)pent-2-enyl]cyclopentancarboxylic acid;
3xcex2-{[(Amino)(imino)methyl]amino}-4xcex1-[1-(-methylcarbonylamino)pentyl]cyclopentancarboxylic acid.
In addition, an exemplary key intermediate, methyl 3-t-butoxycarbonylamino-4-formylcyclopentanecarboxylate 6 (Scheme 4), may be synthesized from methyl 3-hydroxy-4-hydroxymethylcyclopentanecarboxylate 1 (synthesis given in the attached sheets). The primary hydroxyl of 1 may be protected with the TBDMS (tert-butyldimethylsilyl) group; secondary hydroxyl groups upon Mitsunobu reaction (Ph3P, DEAD (diethyl azodi carboxylate), N3H) can give the azido 3; azido 3 is reduced (H2, Pd/C in presence of ((t-boc)2O) to give protected amine 4; primary hydroxyl may be deprotected and on oxidation may give the key intermediate aldehyde 6.
As shown in Scheme 5, the aldehyde 6 may be further coupled with an appropriate allyl or vinyl tributyl tin compound to introduce the moiety for the glycol or glycerol side chain. The scheme has been elaborated with vinyl tributyl tin. The t-boc group in compound 7 may be removed (trifluoroacetic acid) to an amine 8 and the amine may be reacted with bis boc (xe2x80x94OC(xe2x95x90O)C(CH3)3) thiourea to give the protected guanidine 9. The hydroxyl of 9 upon Mitsunobu reaction can give azide 10; the azide can be reduced to amine 11, and further acylated with an appropriate alkyl acid or alkyl sulfonyl chloride to give the desired 12. The double bond of an allyl or vinyl group in the side chain on osmium catalysed dihydroxylation could give compound 13, which upon further deprotections could yield the desired target 14.
Before the deprotection stage in compound 13, the primary hydroxyl may be converted to a tosyl (4xe2x80x94CH3 phenyl SO2) group, conversion of a tosyl to an azide and an azide to an amine give the compounds where R3xe2x95x90CH(OH)CH2NH2, CH(OH)CH(OH)CH2NH2, or CH2CH(OH)CH2NH2.
The synthetic route to prepare the compounds, when R7 is OH, CN, NH2 or NO2 is shown in Scheme 6. The amine 8 upon reaction with cyanogen bromide could give the cyanamine 15; the side chain may be manipulated in the same manner as shown in Scheme 5 to give 16; the further reaction of cyanamine 16 with hydroxylamine hydrochloride, hydrazine or cyanamide could give the appropriate 17, which on deprotection may yield the targets 18.
The reaction of 8 with 2-methyl-1-nitro-2-thiopseudourea leads to 18 (R7xe2x95x90NO2). When R2 is 
the compounds of the type 12 on reaction with P2S5 or Lawsson""s reagent (2,4-bis(4-methoxy phenyl)-1,3-dithia-2,4-diphosphetane-2,4-disulfide) could give compound 19, which on further reactions may be converted to the desired targets.
Other methods to prepare the equivalent of key intermediate 5 are presented in Schemes 8 and 9. The intermediate 25 may be prepared by two different procedures:
i) Scheme 8
The reaction of dimethylmalonate with sodium hydride and then cis 1,4-dichloro-2-butene gives 1,1-dimethyl-3-cyclopentene dicarboxylate 20, which is saponified, decarboxylated and esterified to give the benzyl ester of 3-cyclopentene 22. Compound 22 upon reaction with PhIxe2x95x90NTS give aziridine 23. The aziridine may be opened with bisphenylthiomethane and n-butyllithium to give 24, and 24 upon reaction with copper oxide and copper chloride could yield 25. Compound 25 may be used in Scheme 5 and elaborated in the same manner as 5 to give the desired targets.
ii) Scheme 9
The cyclopentene ester 22 upon an hydroxyamination reaction with chloramine-T in the presence of OsO4 gives 26; the isomers are separated. The desired isomer upon reaction with 4-nitrobenzenesulfonyl chloride gives 27, and the ONS group may be displaced with bisphenylthiomethane to give 24. Conversion to 25 occurs as described above. 
The following Scheme 11 illustrates a procedure for preparing compounds of Examples 6, 7, 20, 26, 27, 28, and 29 represented by the formula: 
6 R=guanidine; Rxe2x80x2=CH2OH isomer A at C-6
7 R=guanidine; Rxe2x80x2=CH2OH isomer B at C-6
20 R=guanidine; 
26 R=guanidine; 
27 R=guanidine; 
28 R=guanidine; 
isomer A
29 R=guanidine; 
isomer B 
The following scheme 12A or scheme 12B illustrates a procedure for preparing compounds of examples 16, 17, 19, 24, and 25 represented by the formula: 
16 R=guanidine, 
17 R=guanidine, 
19 R=guanidine, 
24 R=guanidine, 
25 R=guanidine, 
Fxcx9cCompounds of Examples 6 and 7 
Fxcx9cCompounds of Examples 26, 27, 28 and 29 
Fxcx9cthe Compound of Example 20 
The following Scheme 13 illustrates a procedure for preparing compounds of Examples 8, 9, 18, 21, 22 and 23 represented by the following formula: 
8 R=NH2, Rxe2x80x2=CH2OH
9 R=guanidine, Rxe2x80x2=CH2OH
18 R=NH2, Rxe2x80x2=CH2OCH2C6H5 
21 R=guanidine, 
22 R=NH2, 
23 R=guanidine, 
The following Scheme 14 illustrates a procedure for preparing compounds of Examples 10, 11, 12, 13, 14, and 15 represented by the formula: 